Which statement best describes how proper aggregate gradation affects concrete performance?

• A. It primarily influences surface color.
• B. It has no effect on durability.
• C. Proper gradation reduces voids, improves packing, and increases strength and durability.
• D. It only affects workability, not strength.

Answer: (C)

Proper aggregate gradation means having a well-balanced mix of particle sizes so the grains nestle together rather than leaving large gaps. When the aggregate is well-graded, coarse and fine particles fill the spaces between each other, producing denser packing and fewer voids in the concrete. With fewer voids, less cement paste is needed to fill the remaining gaps, the mixture becomes denser, and its strength and durability improve because there are fewer pathways for water and chemicals to penetrate and for cracks to propagate. Surface color isn’t controlled by how the aggregate is graded, and while gradation can influence workability, the primary benefits come from better packing that leads to higher strength and greater durability.